Schedule time machine backups?

I don't believe there is a simple way to do this. There may be commands in Terminal you can try, but this is not straightforward for most people.

One quick "fix" (*maybe more like a a bandaid) is to eject the backup drive so backups don't start, then remount it to do backups overnight.

There are other things you can do that might help. For instance, if you are using an IMAP email provided (such as MS-Exchange), you can exclude the MS-Exchange email containers because should something happen, the email would all re-download from there server anyway, no need to locally back it up as well. Also, if you have virtual machines (such as Parallels), those are very large and can take many hours to back up, so you could exclude that and instead manually back it up every week or so to a separate backup device. If you are running an anti-virus program (Symantec, for instance), those can slow down backups tremendously. Consider not using such anti-virus software, they aren't really needed on a Mac.

Consider replacing your Time Machine backup drive with an SSD, they are much faster; and use the highest speed cable you can that is compatible with your Mac and backup drive, e.g. Thunderbolt, or USB-C. I have found this can cut the time needed for backups by as much as a factor of ~ 4.

There is a free app you can download called Time Machine Editor which allows you to set up different schedules and interval, been around for years.

https://tclementdev.com/timemachineeditor/